1. Field of the Invention
The present invention relates to a self-displacement detection type cantilever having high sensitivity and high resolution, a cantilever system using the cantilever, a probe microscope including the cantilever system, and an adsorption mass sensor including the cantilever system.
2. Description of the Related Art
In recent years, owing to progress in nanotechnology using a semiconductor process, cantilevers having leaf spring characteristics are used in various devices and sensors to conduct various measurements for shape observation, mass, viscoelasticity, magnetic force, and the like. For example, a scanning probe microscope (SPM) includes a cantilever supported in a cantilever state. A surface of a sample is scanned with a probe provided at a tip end of the cantilever. A tunnel current, an interatomic force, a magnetic force, or viscoelasticity, which acts between the probe and the sample is measured as the amount of bending (displacement) of the cantilever. Therefore, surface shapes or physical properties of the sample may be measured for imaging, and hence the cantilever is used in various fields.
Up to now, an optical lever system for measuring a change in reflection angle of a laser beam emitted to a cantilever to obtain a displacement of the cantilever has been used as a system for detecting the amount of bending of the cantilever, that is, the displacement of the cantilever in the scanning probe microscope. In addition to an external detection method using the optical lever system, a probe microscope using a self-displacement detection type cantilever has been proposed.
For example, a system using a piezoresistive cantilever, that is, a self-detection type SPM probe for measuring a variation in resistance value of a piezo-resistor provided on the cantilever to detect the amount of bending of the cantilever is described in JP 2000-111563 A.
A system using a piezoelectric thin film, that is, a tunnel current detecting apparatus for detecting a fine displacement of a cantilever-shaped fine displacement element which includes the piezoelectric thin film and electrodes by the piezoelectric effect of the piezoelectric thin film is described in JP 05-190617 A.
The self-displacement detection type cantilevers have advantages in that the structures are relatively simpler than the structure of the optical lever system and an alignment operation (operation for adjusting laser beam path) specific to the optical lever system is unnecessary.
The conventional technologies still have the following problems.
That is, in the case of the conventional self-displacement detection type cantilevers, there is a problem that a displacement detection signal has lower sensitivity than in the external detection method using the optical lever system and it is difficult to detect the displacement at high resolution. When high-sensitivity detection is to be performed using the conventional self-displacement detection type cantilever, a detection portion of area of 10 μm unit is required. In recent years, in order to realize an increase in resonant frequency band of the cantilever and high-speed scanning, a reduction in size of the cantilever has been advanced. However, the conventional self-displacement detection type cantilevers have limitations, which is a disadvantage.